67 lines
2.1 KiB
Plaintext
67 lines
2.1 KiB
Plaintext
|
'\" e
|
||
|
|
'\"! eqn | mmdoc
|
||
|
|
'\"macro stdmacro
|
||
|
|
.ds Vn Version 1.2
|
||
|
|
.ds Dt 24 September 1999
|
||
|
|
.ds Re Release 1.2.1
|
||
|
|
.ds Dp Jan 14 18:30
|
||
|
|
.ds Dm 01 frontface
|
||
|
|
.ds Xs 58804 4 frontface.gl
|
||
|
|
.TH GLFRONTFACE 3G
|
||
|
|
.SH NAME
|
||
|
|
.B "glFrontFace
|
||
|
|
\- define front- and back-facing polygons
|
||
|
|
|
||
|
|
.SH C SPECIFICATION
|
||
|
|
void \f3glFrontFace\fP(
|
||
|
|
GLenum \fImode\fP )
|
||
|
|
.nf
|
||
|
|
.fi
|
||
|
|
|
||
|
|
.EQ
|
||
|
|
delim $$
|
||
|
|
.EN
|
||
|
|
.SH PARAMETERS
|
||
|
|
.TP \w'\f2mode\fP\ \ 'u
|
||
|
|
\f2mode\fP
|
||
|
|
Specifies the orientation of front-facing polygons.
|
||
|
|
\%\f3GL_CW\fP and \%\f3GL_CCW\fP are accepted.
|
||
|
|
The initial value is \%\f3GL_CCW\fP.
|
||
|
|
.SH DESCRIPTION
|
||
|
|
In a scene composed entirely of opaque closed surfaces,
|
||
|
|
back-facing polygons are never visible.
|
||
|
|
Eliminating these invisible polygons has the obvious benefit
|
||
|
|
of speeding up the rendering of the image.
|
||
|
|
To enable and disable elimination of back-facing polygons, call \%\f3glEnable\fP
|
||
|
|
and \%\f3glDisable\fP with argument \%\f3GL_CULL_FACE\fP.
|
||
|
|
.P
|
||
|
|
The projection of a polygon to window coordinates is said to have
|
||
|
|
clockwise winding if an imaginary object following the path
|
||
|
|
from its first vertex,
|
||
|
|
its second vertex,
|
||
|
|
and so on,
|
||
|
|
to its last vertex,
|
||
|
|
and finally back to its first vertex,
|
||
|
|
moves in a clockwise direction about the interior of the polygon.
|
||
|
|
The polygon's winding is said to be counterclockwise if the imaginary
|
||
|
|
object following the same path moves in a counterclockwise direction
|
||
|
|
about the interior of the polygon.
|
||
|
|
\%\f3glFrontFace\fP specifies whether polygons with clockwise winding in window coordinates,
|
||
|
|
or counterclockwise winding in window coordinates,
|
||
|
|
are taken to be front-facing.
|
||
|
|
Passing \%\f3GL_CCW\fP to \f2mode\fP selects counterclockwise polygons as
|
||
|
|
front-facing;
|
||
|
|
\%\f3GL_CW\fP selects clockwise polygons as front-facing.
|
||
|
|
By default, counterclockwise polygons are taken to be front-facing.
|
||
|
|
.SH ERRORS
|
||
|
|
\%\f3GL_INVALID_ENUM\fP is generated if \f2mode\fP is not an accepted value.
|
||
|
|
.P
|
||
|
|
\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glFrontFace\fP
|
||
|
|
is executed between the execution of \%\f3glBegin\fP
|
||
|
|
and the corresponding execution of \%\f3glEnd\fP.
|
||
|
|
.SH ASSOCIATED GETS
|
||
|
|
\%\f3glGet\fP with argument \%\f3GL_FRONT_FACE\fP
|
||
|
|
.SH SEE ALSO
|
||
|
|
\%\f3glCullFace(3G)\fP,
|
||
|
|
\%\f3glLightModel(3G)\fP
|